TEMPERATURE SCANNING OF ELECTRICAL ROTATING MACHINES

Abstract

The motor temperature can exceed the normal value because of number of causes as a) operation at line voltage (and frequency) different from rated value b) changes in the motor ventilation because of mounting arrangement or dust accumulation c) more frequent starting duty than was planned d) variation in loading caused by production tolerances of the driven machinery, normal wear, and field adjustment and lastly e) High ambient temperatures. To scan the temperatures at different points of the motor, it is essential that the scanner should be fast and should accurately reflect the temperature. The present work was undertaken to develop a microprocessor based 7- point -temperature scanner which measures the temperature of rotor winding by transmitting the value of temperature with radio link. Since no brushes and sliprings are involved in this scheme, the problem of wear and tear and the infirm contact in the brushes and sliprings is avoided. The developed software demultiplex the channels and gives the value of temperature accurately. The hardware, on the other hand, includes the transmitting circuit and receiving circuit. Since the output of the receiver is TTL compatible, the interfacing with the microprocessor does not require additional hardware. The microprocessor based temperature scanner for rotating machines has been tested with different values of resistance simulated as temperature.